I feel as if I'm starting to repeat myself here, but I'll go over this once more. First, as your camera has only been converted to full-spectrum, that's what it's still focusing. When you install any type of IR filter over the lens, your camera is, in effect, not able to focus anything via AF, as it's not perceiving any visible light. As to say, if you can't see anything through your lens with the filter installed, neither can your camera. Pretty simple.
Why it's blurry is also pretty simple -- IR does not come into focus at the same point as visible light. This is a common, well-documented phenomenon. It is the cause of many optical aberrations, as well, to include any green/cyan/magenta/yellow/purple fringing. You are attempting to focus your lens to light that you cannot see, and your camera's AF has not been calibrated to. You also have no IR designations on your lenses. It should absolutely not be a surprise to you that you can't get a sharp image while shooting filtered.
Diffraction affects IR earlier than visible light. You will see softening from diffraction after f/11, or perhaps even earlier than this. However, due to the type of "IR modification" for which you have opted, and the optics you currently posses, you are stuck with attempting to minimize the circle of confusion with your lenses to increase DoF. As to say, the Pinhole Camera Effect. Due to the earlier onset of diffraction with IR, your images will appear much softer through this means than normal, as well.
To restate: without APO lenses, or without red marks on your optics for different wavelengths of IR, your focus will be off. There is no way for you to scientifically, and repeatably, maintain accurate focus.
I really, really think you need to do some research on this topic. As it stands, I feel as if I am saying the same things over and over to you, but without proper understanding of the physics behind IR photography, you're somewhat confused. I also think that, instead of wasting your time with a full-spectrum camera, you should just shell out the cash and have it re-converted to real-deal Near-IR.